Cost Basis of Stock Spinoff

[2020Emjay2020]

Trying to determine cost basis. Listed as joint tenant on stock I learned about after aunt's death in 2012. Stock went on to spin off 3 companies. Sold the 3 spinoff stocks in 2019 (keeping orig). Is original stock considered a gift or an inheritance? Does it matter? I know value of stock when this arrangement was created in 2000 (says she turned in shares). Have all pertinent info on sale of spin offs. No idea how to calc basis. Appreciate the assistance. Thank you. 

[Anonymous_ · Accepted solution]

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@2020Emjay2020 wrote:

Is original stock considered a gift or an inheritance? 

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If you were a joint tenant with your aunt, then at her death her share (undivided one-half interest) passed to you by operation of law (i.e., you "inherited" her one-half interest which would receive a stepped up basis as of the date of her death). 

You will have to determine the original basis of your one-half, however.